Digital Chip instance declaration syntax:

Axxxx [in_1 in_2 < in_3…in_n > ] [out_1 out_2 < out_3…out_n > ] MyModel

Digital Chip model definition syntax:

.MODEL MyModel d_chip( < Model_Parameters>)

Model definition parameters:

Parameter Name Parameter Description Units Default
BEHAVIOUR Text string describing the logical behavior. The format and commands are described below. — —

Description

This device is used for modeling customized logic behavior using a truth table style approach. The device supports states, and thus allows for the description of sequential logic. The format is specific to Multisim only; it does not follow a standard. The logic description is passed in as text parameter to the behavior model parameter.

Format

The general format is to specify a command and the number of lines in the content that follows the command. Commands are specified using the /command_name convention and must be placed at the beginning of a line.

Because the behavior is passed in as string of text, to tell the netlist parser that every new line of text is actually a continuation of the old line, the plus '+' character is needed on every new line. For example:


.model myCounter d_chip(behaviour= "
+;We have here the beginning of some counter
+/inputs  ~G B A D0 D1 D2 D3
+/outputs Y ~W
+/table 5
+more …
+")

Comments are applied using the semicolon ';' character.

The digital chip device supports three of the six digital signal states that are available in the digital simulator (be careful not to confuse signal states, which are simply digital values correponding to nodes, with logic states, which are representations of some states within a state machine). The three signal states are:

HIGH level with STRONG Strength - denoted as 'H'

LOW Level with STRONG Strength - denoted as 'L'

UNKNOWN Level with HI-IMPEDANCE Strength - denoted as 'Z'